In performance of this project, the contractor will develop a reproducible method of growing large numbers of uniform cultures of tracheal epithelium and associated connective tissues, carefully defining conditions of culture and delineating the biologic characteristics of the tissues when in culture. Cultures will be derived from inbred strains of rats which can serve as both sources of implants and recipients in biological tests of malignant transformation by carcinogens. Techniques of implantation with circumvention of immune mechanisms, if necessary, will be perfected. Known pulmonary carcinogens will be selected for transformation and protocols for exposure to the carcinogens developed. Several different types of criteria for recognition of malignant transformation or for exposure to a carcinogen will be examined and verified by implantation of cultures into hosts as a test of malignancy, defined as the ability of cell derived from the culture to grow invasively, spread, and kill the host.